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  • 1
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    The age of the galactic cosmic rays derived from the abundance of Be-10 (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Satellite measurements of the abundance of the Be-10 isotope in galactic cosmic rays are used to determine the cosmic-ray lifetime for escape. The data are analyzed by employing a technique based on an extensive calibration of a cosmic-ray telescope with the aid of high-energy Be beams accelerated in a bevatron. It is found that the Be-10/Be abundance ratio at 80 MeV/nucleon is 0.028 + or - 0.104. A comparison of this result with calculations based on a homogeneous steady-state model of galactic cosmic-ray confinement and propagation yields an average interstellar density of 0.18 (+0.18, -0.11) atom/cu cm and a corresponding cosmic-ray lifetime of 17 (+24, -8) million years after solar modulation is taken into account. The low average density traversed by the cosmic rays is shown to suggest that the particles may be spending the major part of their existence in regions of very low matter density. The consequences of these results are discussed for models of cosmic-ray propagation in the Galaxy, including such alternatives as propagation in a galactic halo or in regions of interstellar space where the interstellar gas density is very low.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 217
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  • 2
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    The anomalous He-4 component in the cosmic-ray spectrum at below approximately 50 MeV per nucleon during 1972-1974 (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 202; Nov. 15
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  • 3
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    The cosmic-ray age deduced from the Be-10 abundance (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Satellite measurements of the radioactive cosmic-ray species Be-10 are reported. The abundance was measured near 100 MeV per nucleon with high-resolution solid-state telescopes on the IMP-7 and IMP-8 satellites during 1973 and 1974. These two independent measurements yield Be-10/Be ratios of less than 10 percent. Taken together with a galactic propagation model, these results show that the cosmic-ray 'clock' lifetime (most probable value of the order of 20 million years) is significantly greater than that deduced for a nominal interstellar gas density of the order of 1 to 3 atoms per cu cm.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 201; Nov. 1
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  • 4
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    New aspects of the cosmic-ray modulation in 1974-1975 near solar minimum (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Residual cosmic-ray modulation at or near the solar minima of 1965 and 1972-75 is compared on the basis of ground-based and satellite observations of nonrelativistic proton and helium components as well as variations in the relativistic component. It is found that the nonrelativistic fluxes lagged behind the high-energy fluxes to form a hysteresis loop over the period from 1965 to 1973, that the 1975 proton fluxes were about 85% higher than the 1972 level and about 35% higher than the 1965 level, and that the 1975 helium fluxes were about 60% higher than in 1965. Some unique recovery events are discussed, and a time-lag effect dependent on magnetic rigidity is examined which was associated with dynamic changes in the heliosphere. A qualitative explanation is offered for the hysteresis effect.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 213
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  • 5
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    The isotopic composition of galactic cosmic-ray lithium, beryllium, and boron (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The isotopes of cosmic-ray Li, Be, and B near 100 MeV per nucleon have been measured with cosmic-ray telescopes on board the IMP-7 and IMP-8 satellites during 1973 and 1974. The measured isotopic abundances provide a stringent test for models of interstellar propagation and solar modulation. It is found that the isotopic abundances can be explained using a steady-state interstellar propagation model with a 5-g/sq cm leakage mean free path. These results, taken along with Be-10 abundance measurements, indicate a longer lifetime for cosmic rays than that predicted by the usual assumption of an average interstellar density of 1 to 3 atoms per cu cm.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 201; Nov. 1
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  • 6
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    Energy dependence of the Si/Fe ratio in the galactic cosmic rays (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: New measurements are reported of the Si/Fe ratio and the differential energy spectra of galactic cosmic-ray Si and Fe, taking into account the energy range from 35 MeV to 4 GeV per nucleon. The measured data were obtained with the aid of satellite and balloon-borne instrumentation. It is found that for the region below 1 GeV per nucleon the local interstellar spectra computed are consistent with previous galactic cosmic-ray propagation models obtained by Shapiro and Silberberg (1970) and Mason (1972).
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 197; Apr. 15
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  • 7
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    The appearance of super fluxes of quiet time cosmic rays (1978)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: By 1975, it was found that the low-energy H and He fluxes had continued to rise to a point where they exceeded significantly the 1965 levels reported by Garcia-Munoz at al. (1977). In the present paper, it is shown that this trend continued into 1976, and that at least some of the phenomena observed during the 1972-1976 period were not present in 1965.
    Keywords: SPACE RADIATION
    Type: International Cosmic Ray Conference; Aug 13, 1977 - Aug 26, 1977; Plovdiv; Bulgaria
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  • 8
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    The isotopes of neon in the galactic cosmic rays (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper examines the results obtained by the University of Chicago instrument on board the IMP 7 satellite used to measure the abundances of Ne-20 and Ne-22 in the galactic cosmic rays during 1973-1977, over the general energy range of 60-230 MeV per nucleon. It is reported that the instrument shows a mass resolution of 0.7 amu(sigma) which was confirmed by calibrating a backup instrument at the LBL Bevalac with separated beams of neon isotopes. Through the use of standard solar modulation and cosmic-ray propagation models, the cosmic-ray source ratio inferred is Ne-22/Ne-20 = 0.38 = or -0.07 which is significantly greater than the present solar system ratio. It is concluded that propagation effects or cross-section uncertainties cannot account for such a large abundance of Ne-22, and thus this measurement provides evidence that the cosmic rays come from a source region where the Ne-22 abundance is substantially greater than in solar system material.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 232
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  • 9
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    The isotopic composition of galactic cosmic ray Li, Be, and B (1975)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: New measurements are reported of the isotopes of cosmic-ray Li, Be, and B and of the elements C, N, and O, with cosmic ray telescopes on board the IMP-7 and IMP-8 satellites during 1973-74 in the energy range 35-210 MeV/nucleon. High mass resolution and stability together with a set of data more extensive than in previous experiments lead to a clear isotopic separation. The measured isotopic and chemical abundances provide a stringent test for models of interstellar propagation and solar modulation. We find not only that for a steady state propagation and solar modulation model all light isotopes and medium element abundances are explained by 5 g/sq cm average pathlengths, as was earlier found from element analysis, but that also these results, taken along with our Be-10 measurements, indicate a longer lifetime for cosmic rays than predicted by the usual assumption of an average interstellar density of 1 to 3 atoms/cu cm.
    Keywords: SPACE RADIATION
    Type: International Cosmic Ray Conference; Aug 15, 1975 - Aug 29, 1975; Munich
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  • 10
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    The relative abundances of galactic cosmic ray Be-7, Be-9, and Be-10 (1975)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The isotopic composition of galactic cosmic ray Be near 100 MeV/nucleon was measured in interplanetary space with high-resolution solid-state telescopes on the IMP-7 and IMP-8 satellites during 1973-1974. These two independent measurements yield Be-10/Be ratios above 10%. Taken together with the galactic propagation model described in the text, these results show that the cosmic ray 'clock' lifetime (most probable value of roughly 20 million years) is significantly greater than that deduced for a nominal interstellar gas density of about 1 to 3 atoms/cu cm.
    Keywords: SPACE RADIATION
    Type: International Cosmic Ray Conference; Aug 15, 1975 - Aug 29, 1975; Munich
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